Buggy code:
public class NameGridPropertySectionContribution extends AbstractNamePropertySectionContribution { protected ISWTObservableValue observable ; private UpdateValueStrategy labelModelToTargetUpdate ; private UpdateValueStrategy labelTargetToModelUpdate ; private boolean bindingInitialized = false ; private ProcessNamingTools processNamingTools ; private final NotificationListener updateMessage = new NotificationListener ( ) { @ Override public void notifyChanged ( final Notification notification ) { } } ; public NameGridPropertySectionContribution ( final TabbedPropertySheetPage tabbedPropertySheetPage , final ExtensibleGridPropertySection extensibleGridPropertySection ) { } protected void updateEvents ( final Element element ) { } @ Override public String getLabel ( ) { } @ Override public void setEObject ( final EObject object ) { } protected void activateNameListener ( ) { } @ Override public void setSelection ( final ISelection selection ) { } @ Override public void setEditingDomain ( final TransactionalEditingDomain editingDomain ) { } private void updateBindings ( ) { } @ Override public void dispose ( ) { } protected void deactivateNameListener ( ) { } @ Override protected void createBinding ( final EMFDataBindingContext context ) { labelTargetToModelUpdate = new UpdateValueStrategy ( ) ; labelTargetToModelUpdate . setAfterGetValidator ( new org . bonitasoft . studio . common . jface . databinding . validator . UTF8InputValidator ( Messages . name ) ) ; final List < IValidator > validators = new ArrayList < IValidator > ( ) ; <START_BUG> validators . add ( new org . bonitasoft . studio . common . jface . databinding . validator . InputLengthValidator ( Messages . name , ( ( element ) instanceof SequenceFlow ? 0 : 1 ) , 50 ) ) ; <END_BUG> final MultiValidator multiValidation = new MultiValidator ( validators ) ; labelTargetToModelUpdate . setBeforeSetValidator ( multiValidation ) ; labelTargetToModelUpdate . setAfterConvertValidator ( new SpecialCharactersValidator ( ) ) ; observable = SWTObservables . observeDelayedValue ( 400 , SWTObservables . observeText ( text , Modify ) ) ; final IObservableValue nameObservable = EMFEditObservables . observeValue ( editingDomain , element , ELEMENT__NAME ) ; nameObservable . addValueChangeListener ( new IValueChangeListener ( ) { @ Override public void handleValueChange ( final ValueChangeEvent event ) { updatePropertyTabTitle ( ) ; updatePartName ( ( ( String ) ( event . diff . getNewValue ( ) ) ) , Display . getDefault ( ) ) ; } } ) ; ControlDecorationSupport . create ( context . bindValue ( observable , nameObservable , labelTargetToModelUpdate , null ) , LEFT ) ; bindingInitialized = true ; } protected void updatePartName ( final String name , final Display display ) { } protected Runnable refreshPoolEditPart ( final ITextAwareEditPart textAwareEditPart ) { } protected EditPart getPoolEditPart ( final EditPart textAwareEditPart ) { } protected ITextAwareEditPart getTextAwareEditPart ( final IStructuredSelection selection ) { } @ Override protected void editProcessNameAndVersion ( ) { } protected void editDiagramAndPoolNameAndVersion ( ) { } protected void renameDiagramAndPool ( final OpenNameAndVersionForDiagramDialog nameDialog , final DiagramEditor editor , final MainProcess newProcess ) { } protected void editSinglePoolNameAndVersion ( ) { } protected void renamePoolsOnly ( final OpenNameAndVersionForDiagramDialog nameDialog , final DiagramEditor editor , final MainProcess newProcess ) { } }

Fix:
validators . add ( new org . bonitasoft . studio . common . jface . databinding . validator . InputLengthValidator ( Messages . name , ( ( element ) instanceof SequenceFlow ? 0 : 1 ) , 255 ) ) ;